Generally, a hard-disk drive includes a rotating platter with a magnetic surface and a read/write head for reading data from and writing data to the magnetic surface. The read/write head is positioned relative to the magnetic surface using a servo mechanism and is controlled by circuitry for generating and detecting electromagnetic fields on the platter. To store data on the drive, write-channel circuitry encodes binary digital data received from a computing device into magnetic encodings, which are written onto the magnetic surface. To retrieve data from the drive, the servo mechanism first locates the appropriate position, and then read-channel circuitry detects and translates the magnetic encodings at that position into the binary digital data originally stored. Typically, The data on the platter is encoded using magnetic-flux reversals between two adjacent locations on the platter in a scheme known as “non-return-to-zero” (NRZ), where a bit having a value of ‘1’ is stored on the disk as magnetization in one direction, and a bit having a value of ‘0’ is stored as magnetization in the opposite direction. In a typical hard-disk drive, a variety of nonlinearities exist in the recording system, for which the read/write channel compensates. A dibit signal can be used to estimate a variety of non-linear parameters in a hard disk drive system. Such non-linear parameters include non-linear transition shifts, magneto-resistive asymmetry, channel linear density, overwrite, and so forth. These parameters are used for identifying the types and strengths of nonlinear distortions present in the recording channel and developing approaches for mitigating these distortions.